Vinyl Structural Properties 101

[KootK]

I’m going to be evaluating the deflection of some vinyl window frame members. This will be my first time working with vinyl and I’d like to solicit some general advice from anyone that might be familiar with it as a structural material.

Are vinyl material properties highly variable such that, like aluminum, one really needs to pin down the manufacturer’s material specification?

1. Is vinyl a material that undergoes significant creep? Any data available?

2. Does UV exposure degrade vinyl’s material properties? Any data available?

3) Does vinyl weaken when exposed to the light of a full moon?

Like I said, I’m a newborn struggling to stand when it comes to Vinyl. I’ll take anything…

 

[3DDave]

I'm going to go with Yes to most of those questions (except maybe #1, but how much load is on a window?) Most every polymer I've ever seen as a commercial material is mixed with either some other polymer or some other filler, often because UV will slice through most everything, but also to alter stiffness, strength, and appearance.

Worse, some extrusions are co-extrusions where the composition changes across the material section.

http://vinyl-concepts.com/research/vinyl-extrusion/

Best of luck.

 

[NorthCivil]

Not worth it IMO,

For specific projects: if it falls under NAFS, you can do it in vinyl, doesn't need engineering. If it doesnt fall under NAFS, use aluminum.

If its just generic consulting to some vinyl window guys, nothing should need a stamp. Should really do a series of tests to verify performance, it will cost less than all the hours of research you could easily get carried away with

 

[KootK]

@NC: it is a forensic assignment.

 

[TehMightyEngineer]

KootK: Long shot but I did a facility tour of a window manufacturer here in Maine. They had some pretty interesting engineers and I bet they could at least point you in the right direction.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL, CO) Structural Engineer (IL, HI)

 

[epoxybot]

I know you are not suppose to cross post but this might get better feedback from the Polymer Engineering forum.

If this is a NDT forensic assignment, it won't be easy. Ideally you would want the resin supplier and product data. You really want field samples & possibly newly manufactured sample/s for comparison. You want to confirm it is uPVC (unplastisized) and not some unlikely mPVC (modified uPVC).

You can do Shore "D" to oxidized, oxidized/abraded(cleaned) and inner surfaces(unexposed to UV), falling ball impact, perhaps Vicat Softening Temperature and modified tensile/elongation. These would all possibly give some indication of aging or if within generally accepted specified parameters. Shore "D" & falling ball impact are simple & inexpensive, they are fast and give some indication as whether to proceed with more costly Vicat Softening & modified tensile testing and/or more expensive impact tests that have greater correlation to manufacturer testing.

General Physical Properties uPVC: Link
Various PVCs Technical Resource: Link
Good General Technical Paper about PVC formulation: Link

 

[Compositepro]

I would not consider any unreinforced plastic a structural material. The yield strengths are low and creep will occur at stresses that are a fraction of the yield strength. All organic materials slowly degrade due to many factors, sunlight being one of the most important. Most PVC is white or colored due to calcium carbonate filler which lowers cost and makes it stiffer and less prone to creep. Pure PVC is transparent.

 

[TLHS]

I haven't looked, but I was under the impression that window frames were performance tested as assemblies, based on the latest code update talk I went to?